This invention relates to stereo speaker systems, and particularly to systems combining effective bass reproduction with directional stereo response at higher level frequency ranges.
Sound reproduction systems of the prior art have been compelled to deal in compromise fashion with directional and non-directional characteristics of sound waves of differing frequency. Two full range monophonic speakers give incomplete stereo response since they do not deal adequately with directional and non-directional sounds. Bass sounds or sounds at the low range of the frequency scale are substantially non-directional since a listener does not readily detect pressure differentials. When the monophonic speakers are separated for good spacial stereo response many bass sounds are largely unheard because of bass cancellation. This occurs when, for example, there are two separated speaker enclosures each producing identical sound pressure waves primarily in respect to the bass notes involved. As these waves move out, they intersect and in part merge. The usual result is that the maxima pressure wave of one speaker enclosure merges with the minima wave produced from the other. At their points of intercept there is a cancellation of the bass notes.
If the speakers are placed side by side in the listening room, the bass response is improved but at the expense of stereo separation.
Proper placement of the speakers accordingly becomes a compromise in which both bass response and stereo effect are to a degree sacrificed.
Also, in the prior art, excessive vibration in the speaker enclosures has been a problem, to the extent that record turntable components cannot be mounted on a speaker enclosure without vibrating the relatively lightly weighted pickup arm out of a record groove. Moreover, any vibration of a speaker enclosure while reproducing a bass note is exactly 180.degree. out of phase to the movement of the driver cone. This out of phase characteristic distorts the true wave form of the bass note and impairs the acoustical output power of the speaker.
A further problem exists in respect to standing waves. When a bass sound, for example, a low range musical note, leaves a speaker placed squarely along a wall it travels across the room, strikes the opposite wall, and is reflected back toward the speaker. The two waves, the direct and reflected, are 180.degree. out of phase with each other, causing standing waves which produce null or dead areas in a room, the locations of which depends on frequencies involved and the size and configuration of the room.